--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* rfc6803 Camellia Encryption for Kerberos 5
+ *
+ * Copyright (C) 2025 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/slab.h>
+#include "internal.h"
+
+/*
+ * Calculate the key derivation function KDF-FEEDBACK_CMAC(key, constant)
+ *
+ * n = ceiling(k / 128)
+ * K(0) = zeros
+ * K(i) = CMAC(key, K(i-1) | i | constant | 0x00 | k)
+ * DR(key, constant) = k-truncate(K(1) | K(2) | ... | K(n))
+ * KDF-FEEDBACK-CMAC(key, constant) = random-to-key(DR(key, constant))
+ *
+ * [rfc6803 sec 3]
+ */
+static int rfc6803_calc_KDF_FEEDBACK_CMAC(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *key,
+ const struct krb5_buffer *constant,
+ struct krb5_buffer *result,
+ gfp_t gfp)
+{
+ struct crypto_shash *shash;
+ struct krb5_buffer K, data;
+ struct shash_desc *desc;
+ __be32 tmp;
+ size_t bsize, offset, seg;
+ void *buffer;
+ u32 i = 0, k = result->len * 8;
+ u8 *p;
+ int ret = -ENOMEM;
+
+ shash = crypto_alloc_shash(krb5->cksum_name, 0, 0);
+ if (IS_ERR(shash))
+ return (PTR_ERR(shash) == -ENOENT) ? -ENOPKG : PTR_ERR(shash);
+ ret = crypto_shash_setkey(shash, key->data, key->len);
+ if (ret < 0)
+ goto error_shash;
+
+ ret = -ENOMEM;
+ K.len = crypto_shash_digestsize(shash);
+ data.len = K.len + 4 + constant->len + 1 + 4;
+ bsize = krb5_shash_size(shash) +
+ krb5_digest_size(shash) +
+ crypto_roundup(K.len) +
+ crypto_roundup(data.len);
+ buffer = kzalloc(bsize, GFP_NOFS);
+ if (!buffer)
+ goto error_shash;
+
+ desc = buffer;
+ desc->tfm = shash;
+
+ K.data = buffer +
+ krb5_shash_size(shash) +
+ krb5_digest_size(shash);
+ data.data = buffer +
+ krb5_shash_size(shash) +
+ krb5_digest_size(shash) +
+ crypto_roundup(K.len);
+
+ p = data.data + K.len + 4;
+ memcpy(p, constant->data, constant->len);
+ p += constant->len;
+ *p++ = 0x00;
+ tmp = htonl(k);
+ memcpy(p, &tmp, 4);
+ p += 4;
+
+ ret = -EINVAL;
+ if (WARN_ON(p - (u8 *)data.data != data.len))
+ goto error;
+
+ offset = 0;
+ do {
+ i++;
+ p = data.data;
+ memcpy(p, K.data, K.len);
+ p += K.len;
+ *(__be32 *)p = htonl(i);
+
+ ret = crypto_shash_init(desc);
+ if (ret < 0)
+ goto error;
+ ret = crypto_shash_finup(desc, data.data, data.len, K.data);
+ if (ret < 0)
+ goto error;
+
+ seg = min_t(size_t, result->len - offset, K.len);
+ memcpy(result->data + offset, K.data, seg);
+ offset += seg;
+ } while (offset < result->len);
+
+error:
+ kfree_sensitive(buffer);
+error_shash:
+ crypto_free_shash(shash);
+ return ret;
+}
+
+/*
+ * Calculate the pseudo-random function, PRF().
+ *
+ * Kp = KDF-FEEDBACK-CMAC(protocol-key, "prf")
+ * PRF = CMAC(Kp, octet-string)
+ * [rfc6803 sec 6]
+ */
+static int rfc6803_calc_PRF(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *protocol_key,
+ const struct krb5_buffer *octet_string,
+ struct krb5_buffer *result,
+ gfp_t gfp)
+{
+ static const struct krb5_buffer prfconstant = { 3, "prf" };
+ struct crypto_shash *shash;
+ struct krb5_buffer Kp;
+ struct shash_desc *desc;
+ size_t bsize;
+ void *buffer;
+ int ret;
+
+ Kp.len = krb5->prf_len;
+
+ shash = crypto_alloc_shash(krb5->cksum_name, 0, 0);
+ if (IS_ERR(shash))
+ return (PTR_ERR(shash) == -ENOENT) ? -ENOPKG : PTR_ERR(shash);
+
+ ret = -EINVAL;
+ if (result->len != crypto_shash_digestsize(shash))
+ goto out_shash;
+
+ ret = -ENOMEM;
+ bsize = krb5_shash_size(shash) +
+ krb5_digest_size(shash) +
+ crypto_roundup(Kp.len);
+ buffer = kzalloc(bsize, GFP_NOFS);
+ if (!buffer)
+ goto out_shash;
+
+ Kp.data = buffer +
+ krb5_shash_size(shash) +
+ krb5_digest_size(shash);
+
+ ret = rfc6803_calc_KDF_FEEDBACK_CMAC(krb5, protocol_key, &prfconstant,
+ &Kp, gfp);
+ if (ret < 0)
+ goto out;
+
+ ret = crypto_shash_setkey(shash, Kp.data, Kp.len);
+ if (ret < 0)
+ goto out;
+
+ desc = buffer;
+ desc->tfm = shash;
+ ret = crypto_shash_init(desc);
+ if (ret < 0)
+ goto out;
+
+ ret = crypto_shash_finup(desc, octet_string->data, octet_string->len, result->data);
+ if (ret < 0)
+ goto out;
+
+out:
+ kfree_sensitive(buffer);
+out_shash:
+ crypto_free_shash(shash);
+ return ret;
+}
+
+
+static const struct krb5_crypto_profile rfc6803_crypto_profile = {
+ .calc_PRF = rfc6803_calc_PRF,
+ .calc_Kc = rfc6803_calc_KDF_FEEDBACK_CMAC,
+ .calc_Ke = rfc6803_calc_KDF_FEEDBACK_CMAC,
+ .calc_Ki = rfc6803_calc_KDF_FEEDBACK_CMAC,
+ .derive_encrypt_keys = authenc_derive_encrypt_keys,
+ .load_encrypt_keys = authenc_load_encrypt_keys,
+ .derive_checksum_key = rfc3961_derive_checksum_key,
+ .load_checksum_key = rfc3961_load_checksum_key,
+ .encrypt = krb5_aead_encrypt,
+ .decrypt = krb5_aead_decrypt,
+ .get_mic = rfc3961_get_mic,
+ .verify_mic = rfc3961_verify_mic,
+};
+
+const struct krb5_enctype krb5_camellia128_cts_cmac = {
+ .etype = KRB5_ENCTYPE_CAMELLIA128_CTS_CMAC,
+ .ctype = KRB5_CKSUMTYPE_CMAC_CAMELLIA128,
+ .name = "camellia128-cts-cmac",
+ .encrypt_name = "krb5enc(cmac(camellia),cts(cbc(camellia)))",
+ .cksum_name = "cmac(camellia)",
+ .hash_name = NULL,
+ .derivation_enc = "cts(cbc(camellia))",
+ .key_bytes = 16,
+ .key_len = 16,
+ .Kc_len = 16,
+ .Ke_len = 16,
+ .Ki_len = 16,
+ .block_len = 16,
+ .conf_len = 16,
+ .cksum_len = 16,
+ .hash_len = 16,
+ .prf_len = 16,
+ .keyed_cksum = true,
+ .random_to_key = NULL, /* Identity */
+ .profile = &rfc6803_crypto_profile,
+};
+
+const struct krb5_enctype krb5_camellia256_cts_cmac = {
+ .etype = KRB5_ENCTYPE_CAMELLIA256_CTS_CMAC,
+ .ctype = KRB5_CKSUMTYPE_CMAC_CAMELLIA256,
+ .name = "camellia256-cts-cmac",
+ .encrypt_name = "krb5enc(cmac(camellia),cts(cbc(camellia)))",
+ .cksum_name = "cmac(camellia)",
+ .hash_name = NULL,
+ .derivation_enc = "cts(cbc(camellia))",
+ .key_bytes = 32,
+ .key_len = 32,
+ .Kc_len = 32,
+ .Ke_len = 32,
+ .Ki_len = 32,
+ .block_len = 16,
+ .conf_len = 16,
+ .cksum_len = 16,
+ .hash_len = 16,
+ .prf_len = 16,
+ .keyed_cksum = true,
+ .random_to_key = NULL, /* Identity */
+ .profile = &rfc6803_crypto_profile,
+};
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